Low Profile Intervertebral Implant

ABSTRACT

The present invention is directed to a low profile intervertebral implant for implantation in an intervertebral disc space in-between adjacent vertebral bodies. The intervertebral implant includes a plate preferably coupled to a spacer. The plate is preferably formed from a first material and the spacer is preferably formed from a second material, the first material being different from the second material. The plate is preferably sized and configured so that the plate does not extend beyond the perimeter of the spacer. In this manner, the plate preferably does not increase the height profile of the spacer and the plate may be implanted within the intervertebral disc space in conjunction with the spacer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 14/635,480 filed Mar. 2, 2015, which is a continuation of U.S. patent application Ser. No. 13/594,965 filed Aug. 27, 2012, now U.S. Pat. No. 9,005,295 issued Apr. 14, 2015, which is a continuation of U.S. patent application Ser. No. 12/743,098 filed Aug. 25, 2010, now U.S. Pat. No. 8,540,774 issued Sep. 24, 2013, which is a U.S. National Phase of International Application No. PCT/US08/82473 filed Nov. 5, 2008, which claims priority to U.S. Provisional Patent Application No. 60/988,661, filed Nov. 16, 2007, the contents of which are hereby incorporated by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to an intervertebral implant. More specifically, the preferred embodiment of the present invention relates to a low profile fusion intervertebral implant for implantation into the intervertebral disc space between adjacent vertebral bodies.

BACKGROUND OF THE INVENTION

Millions of people suffer from back pain. In some instances, in order to relieve back pain and/or to stabilize the spinal structure, it becomes necessary to fuse adjacent vertebral bodies at one or more levels. One known method for fusing adjacent vertebral bodies is to implant one or more intervertebral implants into the affected disc space.

SUMMARY OF THE INVENTION

A preferred embodiment of the present invention is directed to a low profile intervertebral implant for implantation in an intervertebral disc space between adjacent vertebral bodies. The intervertebral implant includes a plate preferably coupled to a spacer. The plate is preferably sized and configured so that the plate does not extend beyond the perimeter of the spacer. In this manner, the plate preferably does not increase the height profile of the spacer and the plate may be implanted within the intervertebral disc space in conjunction with the spacer.

In another aspect of the preferred embodiment of the intervertebral implant, the plate is coupled to the spacer by one or more arms extending from the plate. The arms are sized and configured to substantially surround and receive the spacer so that the spacer is securely coupled to the plate. The one or more arms may be a circumferential arm that extends from the plate and which completely wraps around the spacer. The circumferential arm may be sized and configured to shrink as a result of temperature variation. Alternatively, the arms may be a plurality of deformable arms sized and configured to receive the spacer. The arms are preferably deformable to substantially surround and compress against the spacer to secure the spacer to the arms. Alternatively, the one or more arms may be selectively interconnected with one another so that the first and second arms may be placed around the spacer and then tightened to operatively couple the spacer to the plate.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of the preferred embodiments of the application, will be better understood when read in conjunction with the appended drawings. For the purposes of illustrating the preferred intervertebral implants of the present application, there is shown in the drawings preferred embodiments. It should be understood, however, that the application is not limited to the precise arrangements and instrumentalities shown. In the drawings:

FIG. 1A illustrates a rear perspective view of an intervertebral implant in accordance with a first preferred embodiment of the present invention;

FIG. 1B illustrates a top perspective view of the intervertebral implant shown in FIG. 1A;

FIG. 2 illustrates a front perspective view of an intervertebral implant in accordance with a second preferred embodiment of the present invention;

FIG. 3A illustrates a rear perspective view of an intervertebral implant in accordance with a third preferred embodiment of the present invention;

FIG. 3B illustrates a front perspective view of the intervertebral implant shown in FIG. 3A;

FIG. 4A illustrates a top perspective view of an intervertebral implant in accordance with a fourth preferred embodiment of the present invention;

FIG. 4B illustrates a bottom plan view of the intervertebral implant shown in FIG. 4A;

FIG. 5 illustrates a partially exploded top perspective view of an intervertebral implant in accordance with a fifth preferred embodiment of the present invention;

FIG. 6 illustrates a partially exploded side perspective view of an intervertebral implant in accordance with a sixth preferred embodiment of the present invention;

FIG. 6A illustrates a cross-sectional view of the intervertebral implant shown in FIG. 6, taken along line 6 a-6 a in FIG. 6 with the intervertebral implant in an assembled configuration;

FIG. 7 illustrates a front perspective view of an intervertebral implant in accordance with a seventh preferred embodiment of the present invention;

FIG. 8 illustrates a rear perspective view of an intervertebral implant in accordance with an eighth preferred embodiment of the present invention;

FIG. 9 illustrates a rear perspective view of an intervertebral implant in accordance with an ninth preferred embodiment of the present invention;

FIG. 10 illustrates a rear elevational view of an intervertebral implant in accordance with a tenth preferred embodiment of the present invention, wherein the intervertebral implant is mounted to a spine;

FIG. 11 illustrates a rear perspective view of an intervertebral implant in accordance with an eleventh preferred embodiment of the present invention; and

FIG. 12 illustrates a rear perspective view of an intervertebral implant in accordance with a twelfth preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Certain terminology is used in the following description for convenience only and is not limiting. The words “right”, “left”, “top” and “bottom” designate directions in the drawings to which reference is made. The words “inwardly” and “outwardly” refer to directions toward and away from, respectively, the geometric center of the device and designated parts thereof. The words, “anterior”, “posterior”, “superior”, “inferior” and related words and/or phrases designate preferred positions and orientations in the human body to which reference is made and are not meant to be limiting. The terminology includes the above-listed words, derivatives thereof and words of similar import.

Referring to FIGS. 1A-12, certain exemplary embodiments of the invention will now be described with reference to the drawings. In general, such embodiments relate to a low profile intervertebral implant 10. It should be understood that while the various embodiments of the intervertebral implant 10 will be described in connection with spinal surgery, those skilled in the art will appreciate that the intervertebral implant 10 as well as the components thereof may be used for implantation into other parts of the body. The same reference numerals will be utilized throughout the application to describe similar or the same components of each of the twelve preferred embodiments of the preferred intervertebral implants described herein and the descriptions will focus on the specific features of the individual embodiments that distinguish the particular embodiment from the others.

Generally speaking, the various embodiments of the intervertebral implant 10 are sized and configured to be implanted between adjacent vertebral bodies V. The intervertebral implants 10 may be sized and configured to replace all or substantially all of an intervertebral disc space D between adjacent vertebral bodies V or only part of the intervertebral disc space D. In addition, the preferred intervertebral implants 10 may be configured to replace an entire vertebral body V and related disc spaces D or multiple disc spaces D in a patient's spine, as is apparent to one having ordinary skill in the art.

The intervertebral implants 10 of each of the preferred embodiments preferably include a plate 40 and a spacer 20. The spacer 20 may include a first insertion end portion 22 (e.g., front end), a second end portion 24 (e.g., rear end) opposite the first insertion end portion 22, a first lateral end 26, a second lateral end 28, an upper surface 30, and a lower surface 32. The spacer 20 is preferably configured and dimensioned for implantation into the intervertebral disc space D between adjacent vertebral bodies V. The spacer 20 is preferably sized and configured to maintain and/or restore a desired intervertebral disc height H between the adjacent vertebral bodies V.

The plate 40 is preferably mounted to the second end portion 24 of the spacer 20 and preferably does not extend beyond the perimeter of the spacer 20. That is, a plate height h_(p) of the plate 40 is preferably no more than a spacer height h_(s) of the spacer 20 at the second end 24 so that the plate 40 does not increase the height profile of the spacer 20. In this manner, the intervertebral implant 10 has a low profile. Additionally, in this manner, the plate 40 may be entirely implanted into the intervertebral disc space D between the adjacent vertebral bodies V such that the plate 40 does not extend beyond an edge of the disc space D.

The upper and lower surfaces 30, 32 of the spacer 20 may include a series of teeth, one or more keels, or other similar projections (not shown) to aid in securing the intervertebral implant 10 to the endplates of the adjacent vertebral bodies V. Alternatively or in addition, the spacer 20 may include one or more windows or channels (not shown) designed to receive bone graft material. For example, the spacer 20 may include one or more vertical windows or channels (not shown) extending through the spacer 20 from the upper surface 30 to the lower surface 32 for insertion of bone graft material such that bone growth is promoted through the vertical windows or channels following implantation of the intervertebral implant 10. Alternatively or in addition, the spacer 20 may have one or more horizontal windows or channels (not shown) extending through the spacer 20 from the first lateral end 26 to the second lateral end 28 for receiving bone graft material.

The upper and lower surfaces 30, 32 of the spacer 20 may include a curved or a tapered surface to help provide the proper shape to the spine or to orient the endplates of the adjacent vertebral bodies V in a desired manner. The particular surface shape and curvature or taper in the anterior-posterior direction as well as between the first and second lateral ends 26, 28 will depend upon the location the implant 10 is intended to be implanted and/or surgeon preferences.

The intervertebral implant 10 may be constructed of any suitable material or combination of materials including, but not limited to polymer (e.g. PEEK), titanium, titanium alloy, stainless steel, Nitinol, tantalum nitride (TaN), allograft bone, bioresorbable material, magnesium, composites, synthetic bone-welding polymers, etc. The plate 40 may be formed of a different material than the spacer 20. For example, the plate 40 may be formed of a metallic material such as, for example, a titanium or a titanium alloy, and the spacer 20 may be formed of a non-metallic material such as, for example, an allograft, a polymer, a bioresorbable material, a ceramic, etc. Alternatively, the plate 40 and the spacer 20 may be formed from the same material. For example, the plate 40 and the spacer 20 may both be constructed of tantalum nitride (TaN).

The plate 40 preferably includes one or more through holes 42 for receiving fasteners 75 such as, for example, one or more bone screws 75, for securing the intervertebral implant 10 to the adjacent vertebral bodies V. The plate 40 may include any number of through holes 42 arranged in any number of combinations. For example, the plate 40 may include two, three, four or more through holes 42 for receiving, preferably, an equal number of bone screws 75. Moreover, the through holes 42 may alternate with one another with one through hole 42 being angled up and the next through hole 42 being angled down (FIGS. 8 and 9), or the through holes 42 on the outside may be angled up while the through holes 42 on the inside may be angled down (FIGS. 5-7, 11 and 12), etc.

The plate 40 of the preferred embodiments includes at least two through holes 42 configured to receive two fasteners 75 for securing the intervertebral implant 10 to the adjacent vertebral bodies V. The at least two through holes 42 preferably diverge so that at least one fastener 75 is secured into the upper vertebral body V while at least one other fastener 75 is secured into the lower vertebral body V so that opposing forces act on the plate 40 and/or vertebral bodies V. Alternatively, the plate 40 may include three through holes 42 configured to receive three fasteners 75. One fastener 75 may penetrate the upper vertebral body V and two fasteners 75 may penetrate the lower vertebral body V, or vice versa. Alternatively, the plate 40 may include four or more through holes 42 configured to receive four or more fasteners 75. In such a configuration, two inner fasteners 75 may penetrate the upper vertebral body V while two outer fasteners 75 may penetrate the lower vertebral body V, or vice versa, or some combination thereof.

The through holes 42 each include a hole axis 43 such that one of the holes 42 exit through the upper surface of the intervertebral implant 10, possibly through the upper surface 30, for engaging the upper vertebral body V while another of the holes 42 exit through the lower surface of the intervertebral implant 10, possibly through the lower surface 32 for engaging the lower vertebral body V. The fastener 75 that extends through the hole 42, preferably along the hole axis 43 forms a fastener angle α with respect to the upper and lower surfaces 30, 32 of the spacer 20 wherein fastener angle α may be in the range between twenty degrees (20°) and fifty degrees (50°), and most preferably between thirty degrees (30°) and forty-five degrees (45°). The fastener angle α may be the same for all of the holes 42 or may be different for each of the holes 42.

The through holes 42 formed in the plate 40 preferably are directed outwardly from the center of the intervertebral implant 10, preferably at a lateral fastener angle Ω. Thus, the through holes 42 preferably extend laterally outward from a center plane 11 of the intervertebral implant 10 at the lateral fastener angle Ω. The lateral fastener angle Ω may be the same for all holes 42 or may be different for each hole 42.

Exit openings 42 a of the through holes 42 may be formed in the plate 40 or in the spacer 20. The through holes 42 may also include one or more threads (not shown) for threadably engaging threads formed on a head portion 75 a of the bone screw 75 in order to secure the bone screws 75 to the plate 40 and to generally lock the position of the bone screws 75 relative to the plate 40 and/or spacer 20.

The intervertebral implant 10 of the preferred embodiments also preferably includes a coupling mechanism 100 for securing the plate 40 to the spacer 20. Generally speaking, the spacer 20 and the plate 40 are coupled together by the coupling mechanism 100 prior to being implanted into the disc space D. However, in certain embodiments, the intervertebral implant 10 may be configured so that the plate 40 may be coupled to the spacer 20 after one of the spacer 20 and plate 40 have been implanted into the intervertebral disc space. Once coupled, the spacer 20 and plate 40 preferably form a solid implant. The coupling mechanism 100 may be any of the coupling mechanisms 100 described herein or their structural equivalents.

Referring to a first preferred embodiment of the intervertebral implant 10 shown in FIGS. 1A and 1B, the coupling mechanism 100 may be in the form of a solid, circumferential arm 102 that extends from the plate 40. The circumferential arm 102 is preferably sized and configured to wrap around and/or to receive the spacer 20 therein. Preferably, the spacer 20 includes a recess 36 formed on the outer surfaces thereof for receiving at least a portion of the circumferential arm 102.

The circumferential arm 102 may be made from a material that deforms or shrinks as a result of being heated or cooled such as, for example, Nitinol or any other suitable material that deforms as a result of temperature variation. In this manner, the plate 40 may be fixed to the spacer 20 by heating or cooling the plate 40, thereby causing the arm 102 of the plate 40 to shrink, which in turn causes the arm 102 to circumferentially engage the spacer 20. This first preferred embodiment of the intervertebral implant 10 is particularly useful since it enables relatively loose tolerances during manufacturing of the spacer 20.

Referring to a second preferred embodiment of the intervertebral implant 10 shown in FIG. 2, the coupling mechanism 100 may be in the form of a split ring 110. That is, the plate 40 may include a pair of arms 112, 114 extending therefrom, wherein the arms 112, 114 are sized and configured to substantially surround the outer circumference of the spacer 20 in order to couple the spacer 20 to the plate 40. The arms 112, 114 are preferably configured so as to be deformable around the spacer 20. That is, the arms 112, 114 are preferably able to deform so that the arms 112, 114 can wrap around and/or squeeze the spacer 20. The intervertebral implant 10 of the second preferred embodiment is not limited to having the pair of arms 112, 114 and may include nearly any number of arms extending from the plate 40 that are deformable to engage and secure the spacer 20 relative to the plate 40.

As best shown in FIG. 2, the split ring 110 may be include an open gap 116 proximate the first insertion end portion 22 of the implant 10 that defines terminal ends 112 a, 114 a of the arms 112, 114. The end portions of the arms 112, 114 proximate the terminal ends 112 a, 114 a are preferably deformable to permit manual clamping of the spacer 20 with the arms 112, 114 to secure the spacer 20 to the plate 40. The gap 116 is not limited to being positioned generally along a midline of the spacer 20 opposite the plate 40 and may be located at nearly any position relative to the plate 40 that permits the arms 112, 114 to deform and clamp or otherwise secure the spacer 20 to the plate 40. For example, the gap 116 may be positioned proximate a corner of the preferred spacer 20 proximate an intersection of the first insertion end portion 22 and one of the first and second lateral ends 26, 28

Referring to FIGS. 3A and 3B, in a third preferred embodiment of the intervertebral implant 10, the split ring 110′ may be sized and configured so that the arms 112′, 114′ may be interconnected to one another at their terminal ends 112 a′, 114 a′ so that, in use, the split ring 110′ may be placed around the spacer 20 and then tightened to operatively couple the plate 40 to the spacer 20. The interconnected arms 112′, 114′ of the split ring 110′ of the third preferred embodiment may be tighten by any means including but not limited to a ratcheting locking mechanism 118, a hose clamp design, etc. Incorporation of the split ring 110′ of the third preferred embodiment enables the plate 40 to accommodate spacers 20 of variable dimensions and compositions. Furthermore, incorporation of the split ring 110′ of the third preferred embodiment may enable the intervertebral implant 10 to be assembled in situ. Other, alternate designs of the plate 40 that allow for the coupling of the plate 40 around the spacer 20 are envisioned. Alternatively, incorporation of the split ring 110′ of the third preferred embodiment may enable the surgeon to incorporate bone packing material as opposed to a pre-formed spacer 20 as described herein and as would be apparent to one having ordinary skill in the art.

Referring to the fourth preferred embodiment of the intervertebral implant 10 shown in FIGS. 4A and 4B, the coupling mechanism 100 may be in the form of a recess 120 preferably extending from the upper surface 30 to the lower surface 32 of the spacer 20 to engage a projection 122 formed on and extending from the plate 40 in an assembled configuration. The recess 120 may be formed in the first and second lateral ends 26, 28 of the spacer 20, in only one of the first and second lateral ends 26, 28, centrally within the spacer 20 or otherwise formed for engagement by the projection 122. For example, as shown, the coupling mechanism 100 of the fourth preferred embodiment is in the form of a dovetail joint, wherein the recess 120 is comprised of recesses 120 extending from the top surface 30 toward the bottom surface 32 proximate the second end 24 and the first and second lateral ends 26, 28, respectively. In this fourth preferred embodiment, the coupling mechanism 100 preferably enables the plate 40 to unidirectionally, slidably engage the spacer 20 by sliding the projection 122 into the recess 120, wherein the projection 122 and recess 120 are formed to prevent the spacer 20 from being engaged with the plate 40 unless the spacer 20 is aligned with the plate 40 and slides along a unitary engagement direction. Alternatively, the projection 122 formed on the plate 40 may be sized and configured to flex across the spacer 20 until the projections 122 substantially fit inside the recesses 120 thereby coupling the spacer 20 to the plate 40 via a press-fit arrangement. It should be appreciated that the locations of the projections 122 and the recesses 120 may be reversed so that the spacer 20 includes the projections and the plate 40 includes the recesses, respectively. In addition, the projections 122 and recesses 120 are preferably sized to align the spacer 20 with the plate 40 such that the top surface 30 of the spacer 20 is generally coplanar with a top surface 40 a of the plate 40 and a bottom surface 32 of the spacer 20 is generally coplanar or aligned with a bottom surface 40 b of the plate 40 in the assembled configuration. Specifically, the projections 122 and the recesses 120 may be tapered to promote the unitary insertion of the spacer 20 into engagement with the plate 40 and alignment of the top and bottom surfaces 40 a, 40 b of the plate 40 with the top and bottom surfaces 30, 32 of the spacer 20 in the assembled configuration.

In addition, the coupling mechanism 100 of the fourth preferred embodiment may include one or more rotatable cams 125, preferably coupled to the plate 40 to lock the spacer 20 to the plate 40 after the spacer 20 is slid onto the plate 40. Alternatively, the one or more rotatable cams 125 may act as a depth stop to prevent the plate 40 and the spacer 20 from sliding completely past one another as the spacer 20 slides onto the plate 40 to engage the projections 122 with the recesses 120, respectively. The cam 125 may be included on either or both of the upper and lower surfaces of either or both of the plate 40 and spacer 20. Preferably, for example, the plate 40 may include one or more cams 125 on the upper and lower surfaces of the plate 40, wherein the cam 125 is sized and configured to engage one or more recesses 126 formed on the upper and lower surfaces 30, 32 of the spacer 20. In use, the plate 40 and the spacer 20 may be coupled to each other by rotation of the cam 125, which may be accomplished by hand or with the benefit of a tool.

Referring to the fifth preferred embodiment of the intervertebral implant 10 shown in FIG. 5, the coupling mechanism 100 may include a screw 130 that is sized and configured to mate with a nut or barrel threaded pin 132 through first and second holes 20 a, 40 c in the spacer 20 and the plate 40, respectively. The screw 130 preferably is sized and configured to mate with the nut or barrel threaded pin 132, which may be inserted from the opposite side of the intervertebral implant 10 to secure the spacer 20 to the plate 40. In use, the screw 130 is threadably engaged to the nut or barrel threaded pin 132, thereby coupling the spacer 40 to the plate 20. As best shown in FIGS. 6 and 6A in a sixth preferred embodiment of the intervertebral implant 10, the screw 130′ may be cannulated to allow inclusion and use of a blocking plate 134 and a set screw 136 to prevent “backing-out” of the fasteners 75.

Referring to the seventh preferred embodiment of the intervertebral implant 10 shown in FIG. 7, the coupling mechanism 100 may be in the form of a swag plate 140 that extends into and engages the distal end of an aperture 142 formed in the spacer 20. The plate 40 comprises two arms 144, 146 in the preferred embodiment that extend from the plate 40 into the aperture 142. In use, the arms 144, 146 may be urged together at their distal ends and inserted into the aperture 142 until the ends of the arms 144, 146 extend through the aperture 142, at which point, the arms 144, 146 are released so that the ends of the arms 144, 146, preferably protrusions formed thereon, engage the distal end of the aperture 142 of the spacer 20. The arms 144, 146 are able to flex or bend proximate their root or proximal ends such that the distal ends of the arms 144, 146 are able to slide through the aperture 142 during assembly. This embodiment enables the plate 40 to engage the spacer 20 from the inside out. In use, this embodiment enables a relatively simple assembly that permits visualization of the anterior/posterior depth of the implant 10 on an X-ray and assembly of the implant 10 in the operating room.

Referring to the eighth preferred embodiment of the intervertebral implant 10 shown in FIG. 8, the spacer 20 may have a generally rectangular or square-shape with the plate 40 mounted proximate a corner of the spacer 20. The plate 40 may be coupled to the spacer 20 by any coupling mechanisms 100 now or hereafter known for such purpose including those described herein. In use, coupling the plate 40 to a corner of the spacer 20, as opposed to one of the long ends, facilitates implanting of the intervertebral implant 10 into the disc space via an oblique angle. This embodiment is preferably used in cervical applications to limit distract the esophagus, via the approach.

Referring to the ninth preferred embodiment of the intervertebral implant 10 shown in FIG. 9, the intervertebral implant 10 includes a relatively narrow lateral footprint. In use, incorporating a narrower lateral footprint enables the intervertebral implant 10 to accommodate smaller sized patients and/or permits smaller incisions to facilitate minimally invasive techniques. The intervertebral implant 10 of the ninth preferred embodiment may be used as a strut so that the remainder of the area around the implant 10 may be packed with bone chips, putty, bone cement, etc. The intervertebral implant 10 of the ninth preferred embodiment may also enable a transpedicular posterior approach. The intervertebral implant 10 may be used for corpectomy as well as discectomy. It should be noted that any of the embodiments disclosed herein may be sized and configured to include a narrower lateral footprint.

Alternatively and/or in addition, as best shown in FIG. 10, a tenth preferred embodiment of the intervertebral implant 10 includes the plate 40 mounted to two spacers 20 such that the implant 10 is able to span one or more vertebral bodies V.

Referring to the eleventh preferred embodiment of the intervertebral implant 10 shown in FIG. 11, the plate 40 may be implanted between adjacent vertebral bodies without a spacer 20 coupled thereto so that the plate 40 may be implanted between adjacent vertebral bodies to maintain the height of the disc space while leaving the surgeon the option as to whether or not to insert an uncoupled spacer 40, bone chips, bone cement, etc. into the remaining portion of the intervertebral disc space D.

The various coupling mechanisms 100 disclosed herein may also include an adhesive bonding for additional coupling of the plate 40 to the spacer 20. That is, various methods of bonding the spacer 20 to the plate 40 may be used in connection with the various coupling mechanisms 100 disclosed herein. These methods, may include, but are not limited to, chemical bonding or process, ultrasound, ultraviolet light, adhesives, bone welding, clamping etc. These methods may be used in addition, or instead of other coupling mechanisms 100.

Furthermore, referring to a twelfth preferred embodiment of the intervertebral implant 10 shown in FIG. 12, the intervertebral implant 10 may be constructed completely of a monolithic material and has angled bores and fasteners 75. The implant 10 and the fasteners 75 are preferably constructed of the same material, which may be, but is not limited to PEEK, titanium, a resorbable polymer, or magnesium. The implant 10 of the twelfth preferred embodiment may be constructed exclusively of a resorbable material that completely resorbes into a patient's body following implantation. Preferably, the intervertebral implant 10 of the twelfth preferred embodiment is made from an allograft material. The intervertebral implant 10 of the twelfth preferred embodiment may be constructed such that the fasteners 75 are formed from synthetic bone material, which may be inserted and thereafter welded to the adjacent vertebral bodies V to thereby couple the intervertebral implant 10 to the adjacent vertebral bodies V. Alternatively, the synthetic bone material fasteners 75 may be constructed without threads in the form of pins. Such synthetic bone fasteners 75 may be non-threaded or include, for example, push-out resistant Christmas tree threads or other types of threads. Incorporation of synthetic bone material fasteners 75 facilitates manufacturing of the intervertebral implant 10 by eliminating metallic components from the implant 10, thereby enabling constructions using exclusively allograft or resorbable materials.

Alternatively, the intervertebral implant 10 of the twelfth preferred embodiment may incorporate a plate 40 coupled to the spacer 20 and welded to the synthetic bone material fasteners 75 by, for example, ultrasound, thereby eliminating the need for any mechanical locking mechanism when the fasteners are mounted in the through holes 42 in an implanted position. In use, manufacturing the spacer 20 from an allograft or resorbable material and incorporating synthetic bone material fasteners 75 results in only the plate remaining within the patient, if any component of the implant 10 remains within the patient, due to the materials resorbing into the patient's body. It should be noted, however, that it is envisioned that synthetic bone material fasteners 75, which may be welded in-situ to the adjacent vertebral bodies V, may be used in connection with any of the intervertebral implants 10 now or hereafter known including any of the various embodiments of the implant 10 described herein.

The intervertebral implants 10 of each of the twelve preferred embodiments are generally sized and configured for anterior insertion, although different configurations may be possible for lateral, antero-lateral or posterior approaches. In addition to the features described, the intervertebral implant 10 may include threaded holes, slots or channels to mate with instruments to facilitate manipulation and insertion.

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, composition of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention.

It will be appreciated by those skilled in the art that various modifications and alterations of the invention can be made without departing from the broad scope of the appended claims. Some of these have been discussed above and others will be apparent to those skilled in the art. For example, the present invention may be employed in different sections of the spinal column, including, but not limited to, the cervical area. 

1. (canceled)
 2. A plate configured to be coupled to a spacer to form an intervertebral implant that is insertable into an intervertebral disc space defined by a first vertebral body and a second vertebral body, the plate comprising: a body portion including a first surface and a second surface offset from the first surface in a first direction, the body portion defining a hole configured to receive a bone fixation element, the hole having an entry opening at least partially defined by the first surface and an exit opening defined at least partially by the second surface, the body portion further including a top and a bottom, the bottom offset from the top in a second direction that is perpendicular to the first direction, the top configured to abut the first vertebral body when the intervertebral implant is inserted into the intervertebral disc space, and the bottom configured to abut the second vertebral body when the intervertebral implant is inserted into the intervertebral disc space; a first arm that extends from the body portion such that a portion of the first arm is offset from the second surface in the first direction, the portion of the first arm including a first arm top and a first arm bottom offset from the first arm top in the second direction; and a second arm that extends from the body portion such that a portion of the second arm is offset from the second surface in the first direction, wherein the first arm and the second arm are sized and configured to securely receive and couple the spacer to the plate, the body portion defines a first height measured from the top of the body portion to the bottom of the body portion in the second direction, the portion of the first arm defines a second height measured from the first arm top to the first arm bottom in the second direction, and the first height is greater than the second height.
 3. The plate of claim 2, wherein the first height is measured along the first surface, the first arm extends from the second surface in the first direction, the first arm projects inward toward the second arm so as to define a terminal end of the first arm, and the second height is measured at the terminal end of the first arm.
 4. The plate of claim 2, wherein the first height is a maximum height of the body portion, and the second height is a minimum height of the first arm.
 5. The plate of claim 4, wherein the portion of the second arm includes a second arm top and a second arm bottom offset from the second arm top in the second direction, the portion of the second arm defines a third height measured from the second arm top to the second arm bottom in the second direction, and the first height is greater than the third height.
 6. The plate of claim 5, wherein when the plate is coupled to the spacer, the intervertebral implant is configured to be inserted in the intervertebral disc space such that the second arm top faces the first vertebral body and the second arm bottom faces the second vertebral body.
 7. The plate of claim 6, wherein when the plate is coupled to the spacer, the intervertebral implant is configured to be inserted in the intervertebral disc space such that the second arm top abuts the first vertebral body and the second arm bottom abuts the second vertebral body.
 8. The plate of claim 6, wherein the second height is equal to the third height.
 9. The plate of claim 6, wherein the third height is a minimum height of the second arm.
 10. The plate of claim 6, wherein the top of the body portion includes a top surface, the bottom of the body portion includes a bottom surface, the first arm top includes a first top arm surface, the first arm bottom includes a first bottom arm surface, the second arm top includes a second top arm surface, the second arm bottom includes a second bottom arm surface, the top surface, the first top arm surface, and the second top arm surface each configured to face the first vertebral body when the plate is coupled to the spacer and the intervertebral implant is inserted in the intervertebral disc space, and the bottom surface, the first bottom arm surface, and the second bottom arm surface each configured to face the second vertebral body when the plate is coupled to the spacer and the intervertebral implant is inserted in the intervertebral disc space.
 11. The plate of claim 6, wherein the first arm includes a first sidewall and a second sidewall that is opposite the first sidewall, the second arm includes a first sidewall that faces the first sidewall of the first arm, the second arm further includes a second sidewall opposite the first sidewall of the second arm, and the second sidewall of the first arm converges toward the second sidewall of the second arm as the first arm extends in the first direction.
 12. The plate of claim 6, wherein both the portion of the first arm and the portion of the second arm are offset from the exit opening in the first direction.
 13. The plate of claim 2, wherein the second height is measured from a first location on the first arm top to a second location on the first arm bottom, the first location is positioned on a surface of the first arm top, the second location is positioned on a surface of the first arm bottom, and the surface of the first arm top is parallel to the surface of the first arm bottom.
 14. An intervertebral implant comprising: a plate including: a body portion including a first surface and a second surface offset from the first surface in a first direction, the body portion defining a hole configured to receive a bone fixation element, the hole having an entry opening defined by the first surface; and an arm that extends from the body portion such that a portion of the arm is offset from the second surface in the first direction, the portion of the arm including an arm top and an arm bottom offset from the arm top in the second direction; and a spacer configured to be coupled to the arm such that the spacer faces the second surface, the spacer including a spacer top and a spacer bottom offset from the spacer top in the second direction, wherein the portion of the arm defines a first height measured from the arm top to the arm bottom in the second direction, the spacer defines a second height measured from the spacer top to the spacer bottom in the second direction, and the second height is greater than the first height.
 15. The intervertebral implant of claim 14, wherein the arm is a first arm, the arm top is a first arm top, the arm bottom is a second arm bottom, the plate includes a second arm, the spacer is configured to be coupled to the second arm, the second arm extends from the body portion such that: 1) the second arm is offset from the second surface in the first direction, and 2) the second arm is offset from the first arm in a third direction that is perpendicular to both the first direction and the second direction, the second arm includes a second arm top and a second arm bottom offset from the second arm top in the second direction, the second arm defines a third height that is measured from the second arm top to the second arm bottom in the second direction, and the second height is greater than the third height.
 16. The intervertebral implant of claim 15, wherein the intervertebral implant is configured to be inserted into an intervertebral disc space, the intervertebral disc space defined by a first vertebral body and a second vertebral body, the intervertebral implant configured to be inserted into the intervertebral disc space such that: 1) each of the first arm top, the second arm top, and the spacer top face the first vertebral body, and 2) each of the first arm bottom, the second arm bottom, and the spacer bottom face the second vertebral body.
 17. The intervertebral implant of claim 16, wherein, the first arm extends from the second surface in the first direction, the first arm projects inward toward the second arm so as to define a first terminal end, the first height is measured at the first terminal end, the spacer includes a first surface that faces second surface of the body portion when the spacer is coupled to the first arm, the second height is measured along the first surface of the spacer, the second arm extends from the second surface in the first direction, the second arm projects inward toward the first arm so as to define a second terminal end, and the third height is measured at the second terminal end.
 18. The intervertebral implant of claim 16, wherein the first height is a minimum height of the first arm, the second height is a maximum height of the spacer, and the third height is a minimum height of the second arm.
 19. The intervertebral implant of claim 16, wherein the spacer top includes a top spacer surface, the spacer bottom includes a spacer bottom surface, the first arm top includes a first top arm surface, the first arm bottom includes a first arm bottom surface, the second arm top includes a second arm top surface, the second arm bottom includes a second arm bottom surface, each of the top spacer surface, the first arm top surface, and the second arm top surface are configured to face the first vertebral body when the spacer is coupled to the first arm and the intervertebral implant is inserted in the intervertebral disc space, and each of the bottom spacer surface, the first bottom surface, and the second bottom surface are configured to face the second vertebral body when the spacer is coupled to the first arm and the intervertebral implant is inserted in the intervertebral disc space.
 20. The intervertebral implant of claim 16, wherein the first arm includes a first inner sidewall that faces the spacer when the spacer is coupled to the first arm, the first arm includes a first outer sidewall that is opposite the first inner sidewall, the second arm includes a second inner sidewall that faces the spacer when the spacer is coupled to the first arm, the second arm further includes a second outer sidewall opposite the second inner sidewall, and the first outer sidewall converges toward the second outer sidewall as the first arm and the second arm each extend in the first direction.
 21. The intervertebral implant of claim 16, wherein the body portion includes a top and a bottom offset from the top in the second direction, the body portion defines a fourth height measured from the top to the bottom in the second direction at the first surface, and the fourth height is greater than the first height. 